Colour of cobalt chloride solution is :

Aluminium gives a green colour bead in the cobalt nitrate charcoal cavity test.Anhydrous ${\mathrm{CoCl}}_2$  is blue and becomes pink when it comes into touch with moisture.

 The charcoal cavity test is based on the fact that metallic carbonates decompose to yield equivalent oxides when heated in a charcoal cavity. The oxides show in the cavity as coloured incrustation or residue.

 Hence, option A is correct.